A general caliper floating type disc brake device has a caliper supported to be movable in a rotation axis line direction of the wheel with respect to a mounting bracket. In this case, the caliper is supported in a freely movable manner by the mounting bracket by a slide mechanism including a pair of slide pins and a sleeve. The caliper has a U-shape that crosses the disc rotor, where an inner pad (friction pad) is supported in a freely movable manner on one side and an outer pad (friction pad) is supported in a freely movable manner on the other side. The disc rotor has an actuator including a piston for pushing the inner pad against the disc rotor arranged on one side.
Therefore, when the driver depresses the brake pedal, the actuator is operated by such tread force, whereby the piston moves forward to push the inner pad against the disc rotor and the caliper moves by the reaction force of when the piston moves forward to push the outer pad against the disc rotor. The disc rotor is thereby sandwiched by a pair of pads, so that the braking force acts on the wheel through the disc rotor.
In the disc brake device described above, when operation fluid is supplied to a fluid pressure chamber at the time of braking, the piston and the caliper move forward toward the disc rotor to push the pair of pads against the disc rotor. At the time of fluid pressure release from the fluid pressure chamber, the piston and the caliper can move backward to move away from the disc rotor by a retractor mechanism such as a rubber.
Such disc brake device including the retractor mechanism is described in patent literature 1. The disc brake device described in patent literature 1 includes a slide pin for guiding the movement of the caliper at the time of braking, and a retraction seal accommodated in a seal groove formed in the slide pin, where the caliper returns to the state before the movement by the elastic restoring force of the retraction seal at the time of depressurization after the braking.